A warewashing machine is a utility dishwasher used in many restaurants, healthcare facilities and other locations to efficiently clean and sanitize cooking and eating articles, such as, dishes, pots, pans, utensils and other cooking equipment. Articles are placed on a rack and provided to a washing chamber of the warewashing machine. In the chamber, rinse agents and cleaning products are applied to the articles over a predefined period of time referred to as a “wash cycle.” A wash cycle includes a cleaning cycle and a rinsing cycle. At least one cleaning product is applied to the articles during the cleaning cycle. The cleaning product is typically a chemical solution formed by dissolving one or more component chemical products in water. The term component chemical product is used broadly to encompass, without limitation, any type of detergent, soap or any other product used for cleaning and/or sanitizing.
At least one rinse agent is applied to the articles during the rinsing cycle. The rinse agent is typically water with one or more wetting and/or sanitizing agents. The article racks contain holes that enable the cleaning product and rinse agent to pass through the racks during the cleaning and rinsing cycles, respectively. At the end of the wash cycle, the rack is removed from the washing chamber so that other racks carrying other articles may be moved into the washing chamber. The wash cycle is then repeated for each of these subsequent racks. Wash cycles may be customized for specific types of racks and the articles that the racks carry.
The cleaning products (hereinafter, “chemical solutions”) applied to the articles by the warewashing machine are formed and contained in a solution tank typically located on the underside of the warewashing machine. A wash module is provided above the solution tank and in the lower portion of the washing chamber. The wash module extracts a chemical solution from the tank and applies the solution to the articles contained in the rack during the cleaning cycle. Following the cleaning cycle, a rinse module, which is provided in the upper portion of the washing chamber, administers the rinsing cycle by applying a rinse agent to the articles thereby rinsing the chemical solution from the articles.
Percent concentration of each individual component chemical product within a chemical solution being used by a warewashing machine to clean and sanitize articles at a public facility is governed by various food and health regulations. The percent concentration of a particular component chemical product relative to a formed chemical solution is proportional to the mass of the component relative to the mass of water in the chemical solution. One generally accepted method for complying with these regulations involves controlling input of component chemical product(s) into the chemical solution based on conductivity measurements of the solution. Conductivity of a chemical solution is generally defined as the electrical behavior of the solution, and therefore, is defined herein as a combination of the inherent electrical behavior associated with the water and the electrical behavior associated with the component chemical product(s) forming the solution.
To meet the above-noted various food and health regulations, warewash controllers are employed to oversee operations performed during the wash cycles of conventional warewashing machines. Warewash controllers are often added to warewashing machines after the machines are deployed into a production environment in which the machines are intended for use. The warewash controllers are communicatively coupled to the rinse and wash modules such that control over operations of these modules is administered by the controller. The warewash controller is also communicatively coupled to a component dispenser and operable to control the component dispenser to dispense specified amounts of a component chemical product to the solution tank and/or wash chamber. The warewash controller senses information related to operation of the warewashing machine and uses this sensed information to operate the component dispenser in such a manner that the various food and health regulations are complied with.
A warewash controller may utilize either inductive probes or conductivity cells to sense information related to conductivity of a chemical solution within the solution tank. Typically, these probes or cells gather such information by sampling, preferably multiple times, a predetermined volume of the chemical solution to generate therefrom a voltage indicative of the conductivity of the chemical solution. The warewash controller then links this voltage to an associated conductivity reading for the chemical solution. The conductivity readings are averaged by the warewash controller to determine an average conductivity over a specified period in time. The warewash controller uses this average conductivity to estimate the percent concentration of the component chemical product relative to water in the solution. If the percent concentration of the component chemical product is below a range prescribed by governing regulations, the warewash controller controls dispensing of that component chemical product in order to force the percent concentration to the prescribed range.
The above-mentioned conventional process of controlling detergent dispensing based on an estimated percent concentration has been an effective mechanism for complying with regulations throughout the years. However, this process is problematic in that such control is based on somewhat inaccurate readings with respect to the estimated percent concentration of component chemical products in the chemical solution. As noted above, water is associated with an inherent conductivity, and this inherent conductivity is included in the conductivity readings derived from voltages generated in the inductive probes or conductivity cells. As such, the resulting estimated percent concentration of a component chemical product relative to water is often inaccurate insofar as this estimated percent concentration for the component chemical product is based on the electrical behavior of not only the component chemical product, but also the inherent conductivity of water into which the component chemical product is dissolved.